1. Field of the Invention
This invention relates to a pre-inked hand stamp of the kind making use of an imaging member having a microporous structure impregnated with ink and capable under compression of releasing ink gradually so that imprints can be made of indicia, or type elements, presented in relief on the imaging member. More particularly, the invention relates to several improvements in such as hand stamp which provide for a more stable operation and a more even imprint.
2. State of the Art
Pre-inked hand stamps typically include a platen to which an imaging member is fixed, a case that houses the platen, a handle disposed over the case and a shaft or stem interconnecting the handle and the platen. A spring holds the handle assembly in an upward position with the platen and an imaging member entirely inside the case. The handle assembly is displaceable downward against the spring by pressure of a user""s hand on the handle so that the imaging member will mark a surface underlying the case. The distance of downward travel, or stroke, of the handle assembly is limited by abutment of a stop member carried with the handle against a stop member supported by the case, and at least one of these stop members is made adjustable in location lengthwise of the stem so that the permitted stroke length of the assembly can be changed when need occurs. A light imprint results if the downward stroke does not compress the stamp indicia sufficiently, while an overly dark or smudged imprint may result if the indicia are compressed too much.
Generally, as ink is depleted from the microporous imaging member, it is desirable to lengthen the stroke to create a darker image. It is important, too, that inadvertent or unintended changes of the stroke adjustment of the handle assembly be avoided.
Since users of a hand stamp will press its handle downward with forces that vary greatly in magnitude and also vary in direction from straight up and down, the quality of the imprints to be obtained in uses of the stamp is influenced by the degree to which its structures will function correctly regardless of the magnitude and the angle of the force applied to the handle by a user.
U.S. Pat. No. 5,377,599 discloses a pre-inked hand stamp which includes a platen carrying a microporous imaging member, a case housing the platen and imaging member, a handle extending upward of the case, and a stem interconnecting the handle with platen, forming a movable assembly. A spring is mounted about the stem between the handle and the case thereby biasing the platen in an upward position inside the case. A stop member inside the handle and a coacting stop member seated relative to an upper portion of the case are spaced apart when the spring biases the platen upward. Upon downward displacement of the handle, the stops abut each other to limit such displacement. One of the stop members is adjustable in location lengthwise of the stem to change the permitted distance of displacement. Several different arrangements are shown for adjusting the location of one of the stops.
Disadvantages of the ""599 patent are that the assembly is somewhat complex making assembly difficult, and that lateral movement of the stem and handle relative to the case is not adequately prevented. Several other structural elements of the stamp operate to result in an uneven stamping.
It is therefore an object of the invention to provide a pre-inked hand stamp which is relatively simple in construction and relatively easy to assemble.
It is also an object of the invention to provide a pre-inked hand stamp which limits lateral movement of the stem and handle relative to the case.
It is another object of the invention to provide a pre-inked hand stamp which incorporates other structural features which operate to provide a more even stamping.
In accord with these objects which will be discussed in detail below, the pre-inked hand stamp of the present invention includes a platen carrying a microporous imaging member on its lower portion and having a centrally located threaded stem extending upward from its upper portion; an upper case member having an open bottom and a centrally located opening in its top, the stem of the platen extending through the centrally located opening; a spring and an adjustable stopping assembly coaxially mounted on the stem; and a handle threadably coupled to the end of the stem.
According to the invention, the adjustable stopping assembly includes three members: a lower base member which is mounted in the central opening of the upper case member, a rotatable member which is mounted on the lower base member, and an upper threaded member which is mounted in the rotatable member. The spring is mounted between the upper threaded member and the lower rotatable member.
The lower base member is a stepped cylinder, the lower portion of which has a spline which engages a groove in the central opening of the upper case member. A step on the lower base member is provided with at least one click-stopping bump. The rotatable member is a cylinder with a lower knurled flange and a base having a plurality of click-stopping depressions. The interior surface of the rotatable member is provided with at least one vertical groove. The upper threaded member is a stepped cylinder, the lower portion of which is dimensioned to fit inside the rotatable member and is provided with at least one spline which engages the at least one vertical groove. The upper portion of the threaded member has a diameter which prevents it from entering the rotatable member and has a threaded opening which engages the threaded stem. The handle has a threaded boss which engages the stem and which is received by a depression in the upper portion of the threaded member.
Rotation of the rotatable member, by gripping the knurled flange, causes rotation of the upper threaded member, by virtue of the spline and groove coupling, which results in movement of the upper threaded member along the threaded stem. This moves the upper portion of the threaded member relative to the rotatable member changing the permissible stroke of the handle.
The fact that the upper threaded member engages the interior of the rotatable member with a spline and groove arrangement prevents lateral movement of the stem relative to the upper case member. The click-stopping bump(s) and the click-stopping depressions prevent unintended rotation of the rotatable member and provide an audible indication of the magnitude of the change of stroke.
According to additional aspects of the invention, the imaging member is provided with rounded edges; the platen is reinforced with orthogonal ribs; and the handle is provided with a concavity which allows the stamp to stand upside down on the handle. As with other hand stamps of this type, the assembly also preferably includes a lower case member which snap-fits to the bottom of the upper case member to prevent dirt from damaging the imaging member when not in use and to inhibit evaporation of ink.
Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures.